Transcriptional response of laboratory-reared Mexican fruit flies (Anastrepha ludens Loew) to desiccation.

Confronting environments with low relative humidity is one of the main challenges faced by insects with expanding distribution ranges. Anastrepha ludens (the Mexican fruit fly) has evolved to cope with the variable conditions encountered during its lifetime, which allows it to colonise a wide range of environments. However, our understanding of the mechanisms underpinning the ability of this species to confront environments with low relative humidity is incomplete. In this sense, omic approaches such as transcriptomics can be helpful for advancing our knowledge on how this species copes with desiccation stress. Considering this, in this study, we performed transcriptomic analyses to compare the molecular responses of laboratory-reared A. ludens exposed and unexposed to desiccation. Data from the transcriptome analyses indicated that the responses to desiccation are shared by both sexes. We identified the up-regulation of transcripts encoding proteins involved in lipid metabolism and membrane remodelling, as well as proteases and cuticular proteins. Our results provide a framework for understanding the response to desiccation stress in one of the most invasive fruit fly species in the world.

Phytosanitary cold treatment of cherry tomatoes infested with Bactrocera dorsalis, Zeugodacus cucurbitae, and Zeugodacus tau (Diptera: Tephritidae).

Fruit flies attack numerous crops, including cherry tomatoes (Solanum lycopersicum var. cerasiforme). The potential presence of the immature stages of fruit fly species inside tomatoes during export hinders their international market access. Therefore, phytosanitary treatment must be performed before export to prevent fruit fly species from entering countries where they are not naturally found. We developed a phytosanitary cold disinfestation treatment protocol to eliminate oriental fruit fly (Bactrocera dorsalis Hendel), melon fly (Zeugodacus cucurbitae Coquillett), and pumpkin fruit fly (Zeugodacus tau Walker) concealed inside cherry tomatoes without causing critical damage to the fruit. We determined that the third instar of Z. cucurbitae exhibited the highest cold tolerance among the various development stages of the three fruit fly species. Thus, we performed a small-scale disinfestation test on Z. cucurbitae in two cultivars of tomato. We achieved complete disinfestation after 15 days of cold treatment at 1°C-1.5°C. The confirmatory test revealed the elimination of more than 80,000 treated third instar of Z. cucurbitae in each tomato variety. The developed phytosanitary cold treatment allows the tomatoes to retain their commercial value. This study provides a standard phytosanitary cold treatment protocol for cherry tomatoes, ensuring the disinfestation of fruit flies before their export to international markets.

Testing the potential of entomopathogenic nematodes in attract-and-kill and autodissemination approaches in the control of Queensland fruit fly, Bactrocera tryoni.

BACKGROUND: Many studies have demonstrated that tephritid fruit fly larvae are highly susceptible to entomopathogenic nematodes (EPNs) and may become infected as they enter the soil to pupate. However, the susceptibility of adult tephritids and their suitability as EPN targets have been less studied. We performed laboratory assays with 12 Australian EPN strains of Heterorhabditis bacteriophora, Heterorhabditis indica and Heterorhabditis zealandica in adults of the Queensland fruit fly, Bactrocera tryoni. Infective juveniles were delivered in a yeast hydrolysate solution that is attractive to flies. We also measured the flight ability of adults up to 3 days after treatment. RESULT: Flies that consumed the EPN-yeast preparation experienced 72.8-84% mortality. Between 33.5% and 46.2% of EPN-treated adults were still able to fly before death following treatment, mostly within the first day, thereby contributing to EPN dispersal. Another 31.9-39.9% of EPN-treated flies that were unable to fly died as a result of EPN treatment. Overall, >65% of flies that died following EPN treatment had visible signs of infection and EPN reproduction. CONCLUSION: Our study is foundational to the development of attract-and-kill and autodissemination approaches involving EPNs in fruit fly control. Furthermore, H. indica and H. zealandica strains showed the highest potential as biocontrol agents against adult flies. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Dynamics of Bactrocera dorsalis Resistance to Seven Insecticides in South China.

Bactrocera dorsalis is a highly invasive and destructive pest distributed worldwide. Chemical insecticides remain the primary measure for their control; however, this species has already developed resistance to several insecticides. In recent years, there have been several reports of monitoring B. dorsalis resistance in China, but continuous monitoring results are lacking and do not even span a decade. In this study, we monitored the dynamics of resistance to seven insecticides among 11 geographically distinct Chinese populations of B. dorsalis (2010-2013; follow-up in 2023). The 11 populations were found to adapt rapidly to antibiotic insecticides (spinosad, emamectin benzoate, and avermectin), reaching high levels of insecticide resistance in several areas. Overall, a decreasing trend in resistance to organophosphorus insecticides (chlorpyrifos and trichlorfon) was observed, whereas pyrethroid (beta-cypermethrin and cyhalothrin) resistance trends were observed to both increase and decrease. The monitoring of field resistance among different B. dorsalis populations over the duration of this study is important for improving the efficiency and sustainability of agricultural pest management, and the results provide a scientific basis for the development of more effective resistance management strategies.

The biogeographic patterns of the olive fly and its primary symbiont Candidatus Erwinia dacicola across the distribution area of the olive tree.

The olive fly, Bactrocera oleae (Rossi, 1790), is the major insect pest of olives attacking both cultivated and wild olive. Bactrocera oleae carries a primary and vertically transmitted symbiont, the bacterium Candidatus Erwinia dacicola. As any primary symbiont, it plays an important role in the reproduction and lifespan of the fly. The genetic 16S rRNA diversity of the primary symbiont and the mitochondrial haplotype variation of the insect host were simultaneously examined in 54 olive fly populations. The aim was to unravel the biogeographic patterns of this economically relevant host-bacteria interaction across a wide distribution area. Three symbiont haplotypes were identified. The primary symbiont showed a lower haplotype diversity than that of its host, a characteristic indicative of a long-term interaction. A significant genetic and geographic association between host and primary symbiont was observed, with an East-West genetic differentiation pattern in the Mediterranean basin, coinciding with the historical genetic distribution of the olive tree. The study shows promise, informing and aiding the development of future tools for the control of the olive fly.

Molecular Characterization, Evolution and Expression Analysis of Ammonium Transporter from Four Closely Related Bactrocera Species (Tephritidae).

Numerous insects are attracted to low levels of ammonia, utilizing it as a cue to locate food sources. The Ammonium Transporter (Amt), a highly conserved, atypical olfactory receptor, has been shown to mediate the detection of ammonia in insects. While the attraction of Tephritidae to ammonia is well established, knowledge about the Amt in this family is limited. The species Bactrocera dorsalis (Hendel 1912), Bactrocera cucurbitae (Coquillett 1899), Bactrocera correcta Bezzi 1916 and Bactrocera tau (Walker 1849), which are common agricultural pests within Tephritidae, exhibit numerous ecological similarities, offering a solid foundation for studying Amt characteristics in this family. In this study, we elucidated the sequences, evolutionary relationships, and expression patterns of Amt in these four species. The results indicated that these Amts share the same open reading frame, containing 1770 bp that encode a protein of 589 amino acid residues. These Amt proteins exhibit the typical structural characteristics of Amts, including an 11-transmembrane domain with an extracellular N-terminus and an intracellular C-terminus. They also have the ability to form trimers in the membrane. Additionally, they contain three conserved amino acid residues essential for ammonia transport: A189, H195, and H352. Phylogenetic and expression pattern analyses showed that they are highly conserved in Diptera and are significantly expressed in antennae. This study is the first report characterizing the Amt gene in four Tephritidae species. These findings provide a foundation for further exploration into the roles of these genes in their particular biological contexts.

Male condition and seminal fluid affect female host-marking behavior in the Mexican fruit fly.

Mating and the transfer of seminal fluid components including male accessory glands (MAGs) proteins can affect oviposition behavior in insects. After oviposition, some species of fruit flies deposit a host-marking pheromone (HMP) on the fruit that discourages oviposition by other females of the same or different species or genus and reduces competition between larvae. However, we know very little about how mating, receiving seminal fluid, or male condition can affect female host marking behavior. Here, we tested how the physiological state of females (mated or unmated), the receipt of seminal fluid, and the condition of the male (wild or sterile) affect oviposition and host-marking behavior (HMB) in Anastrepha ludens (Diptera: Tephritidae). We also determined the efficiency of the host-marking pheromone from mated or unmated females in deterring oviposition. In a further examination of how seminal fluid may be affecting HMB we assessed if there were differences in the size of wild or sterile MAGs and the protein quantity transferred during mating. Our results indicate that receiving seminal fluid increased egg laying and increased time invested in host-marking (HM). Unmated females laid fewer eggs than mated females but invested the same amount of time in depositing host-marking pheromone, which had similar effectiveness in deterring oviposition as that of mated females. Females that mated with sterile males laid the same number of eggs as females that mated with wild males but spent less time depositing host-marking pheromone, which suggests that females detect the condition of the male and invest less in marking hosts. Finally, sterile males had larger accessory glands and transferred more MAGs proteins during mating compared to wild males. Seminal proteins could be manipulating HM behavior and female investment into their current reproductive effort. We are only beginning to understand how male condition and seminal fluid can affect female physiology and maternal investment in HMP.

Evidence for transient deleterious thermal acclimation in field recapture rates of an invasive tropical species, Bactrocera dorsalis (Diptera: Tephritidae).

Knowing how environmental conditions affect performance traits in pest insects is important to improve pest management strategies. It can be informative for monitoring, but also for control programs where insects are mass-reared, and field-released. Here, we investigated how adult thermal acclimation in sterile Bactrocera dorsalis affects dispersal and recapture rates in the field using a mark-release-recapture method. We also considered how current abiotic factors may affect recapture rates and interact with thermal history. We found that acclimation at 20 or 30 °C for 4 d prior to release reduced the number of recaptures in comparison with the 25 °C control group, but with no differences between groups in the willingness to disperse upon release. However, the deleterious effects of acclimation were only detectable in the first week following release, whereafter only the recent abiotic conditions explained recapture rates. In addition, we found that recent field conditions contributed more than thermal history to explain patterns of recaptures. The two most important variables affecting the number of recaptures were the maximum temperature and the average relative humidity experienced in the 24 h preceding trapping. Our results add to the handful of studies that have considered the effect of thermal acclimation on insect field performance, but notably lend support to the deleterious acclimation hypothesis among the various hypotheses that have been proposed. Finally, this study shows that there are specific abiotic conditions (cold/hot and dry) in which recaptures will be reduced, which may therefore bias estimates of wild population size.

Comparative adult preference-larval performance relationship between a specialist and a generalist tephritid: Implication for predicting field host-range.

Phytophagous insects differ in their degree of specialization to their host plants. It ranges from monophagous or oligophagous species that can only develop on a single host plant, or family of host plants, to extremely polyphagous species that can develop on plants from many distinct botanical families. The aim of this study was to compare the larval performance and adult preference of a highly generalist species, the Queensland fruit fly (Bactrocera tryoni) and a highly specialist species, the breadfruit fruit fly (B. umbrosa) among several fruits covering both species' host range. (i) larval performance was tested on 16 fruit species, and (ii) a female preference was tested on a subset of five fruit species. In addition, (iii) a field survey was carried out on 11 fruit species. B. umbrosa infested only Artocarpus fruits in the field. Accordingly, B. umbrosa larvae survived and developed only on fruits belonging to the Artocarpus genus. Female B. umbrosa did not lay their eggs on non-Artocarpus fruits, except Terminalia catappa. Female B. tryoni, on the other hand, made little selection between the fruits tested, and its larvae developed on 13 of the 16 fruit species tested. The larval performance of both species, adjusted when tested by female preference, predicted in large part the fruit infestation in the field. These data are essential to better estimate invasion risk where the species are not established.

Evaluating impacts of radiation-induced sterilization on the performance and gut microbiome of mass-reared Mediterranean fruit fly (Ceratitis capitata) in Hawai'i.

Sterile insect technique (SIT) is a useful strategy for preventing and mitigative establishment of invasive insect species. SIT of the pest tephritid Mediterranean fruit fly, Ceratitis capitata (Wiedemann, 1824)WiedemannWiedemann, has been effective in preventing population establishment in vulnerable agricultural areas of the United States. However, irradiation-induced sterilization can have detrimental impacts resulting in reduced performance metrics. Mediterranean fruit fly males reared for SIT have been shown to have differences in their microbiomes relative to other population sources, which has been postulated to be a factor in how well flies compete with wild conspecifics. To identify baseline performance metrics on the effects of irradiation on the gut microbiome of mass-reared flies in Hawai'i, a study was performed to assess performance metrics and microbiome (bacterial 16S rRNA) variation across multiple timepoints. Mediterranean fruit fly pupae were selected from mass-reared trays intended for release, and paired samples were either irradiated or remained as controls and transported to the laboratory for evaluation. Irradiated flies exhibited fewer successful fliers, more rapid mortality rates, and were less active relative to control nonirradiated flies. Contrary to initial expectations, irradiation did not exert substantial impacts on the composition or diversity of bacterial reads. Samples were primarily comprised of sequences classified as Klebsiella and there were low levels of both read and taxonomic diversity relative to other 16S surveys of medfly. Although this study does not demonstrate a strong effect of irradiation alone on the Mediterranean fruit fly microbiome, there are several explanations for this discrepancy.

Effect of temperature and humidity on insect DNA integrity evaluated by real-time PCR.

Insects collected in dry traps can degrade rapidly, especially in warm, humid environments where many biodiversity and biosecurity surveillance activities are undertaken. Degradation can severely impact diagnostics, as trap catches can become difficult to identify to species level using morphological characters or, of increasing importance, molecular approaches. This is especially problematic for biosecurity surveillance of exotic tephritid fruit flies, where diagnostics are heavily reliant on morphological characters. We tested the effects of differing temperature and humidity conditions on mock samples of tephritid fruit flies in a controlled environment and compared our results to field trap catches. DNA degradation was quantified using real-time PCR assays, including one assay newly developed and tested here. We observed a correlation between increasing DNA degradation and increasing temperature and humidity. The greatest DNA degradation occurred under combined high humidity (90% relative humidity) and constant high temperature (35 °C). Unexpectedly, fluctuating temperature did not have a significant impact on DNA. Other factors, such as trap design, time in the field, and rainfall, did not significantly correlate with DNA quality across the field samples tested. When plotted against mock samples, field samples clustered together, with no clear pattern or predictability regarding the quantity of DNA preserved, indicating other untested environmental variables may be at play. Predictably, increased exposure time was found to have a detrimental effect on DNA quality for all treatments. These findings will improve the delivery of surveillance activities through the implementation of shorter trap clearance timeframes and improved trap designs and procedures.

Persistence of widespread moderate Spinosad resistance among wild melon fly (Zeugodacus cucurbitae) and oriental fruit fly (Bactrocera dorsalis) populations on the major Hawaiian islands.

BACKGROUND: Insecticide resistance among invasive tephritid fruit flies poses a great risk to national food security and has the potential to disrupt quarantine and eradication programs, which rely on the efficacy of Spinosad to prevent widespread establishment in North America. During 2022 to 2023 we surveyed the extent of Spinosad resistance of two key species, oriental fruit fly Bactrocera dorsalis, and melon fly Zeugodacus cucurbitae, from 20 sites across five Hawaiian Islands including Kaua'i, O'ahu, Maui, Molokai and the "Big Island" (Hawai'i). RESULTS: We used topical thoracic applications of eight concentrations of Spinosad ranging from 0.028 to 3.6 mg/mL to evaluate the lethal concentration (LC50 and LC99) required to kill wild-caught males. Resistance ratios (RR) were calculated by comparing the LC50 of wild flies to laboratory susceptible lines maintained in colony. Our results identified at least two new sites of concern for melon fly resistance on the Big Island, and at least four sites of concern for oriental fruit fly, all of which were located on the Big Island. At these locations RRs were >5. On O'ahu, melon fly RRs were >10. CONCLUSIONS: The persistence of Spinosad resistance is concerning, yet it is a reduction compared to the values reported previously and before changes to Spinosad use recommendations by local extension agents beginning in 2017. For oriental fruit fly, these RR values are the highest levels that have been detected in wild Hawai'i populations. These data suggest that expanded Spinosad reduction and replacement programs are warranted given the ongoing issues with Spinosad resistance in Hawai'i and expansion in the number of species affected. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Towards a better future for DNA barcoding: Evaluating monophyly- and distance-based species identification using COI gene fragments of Dacini fruit flies.

The utility of a universal DNA 'barcode' fragment (658 base pairs of the Cytochrome C Oxidase I [COI] gene) has been established as a useful tool for species identification, and widely criticized as one for understanding the evolutionary history of a group. Large amounts of COI sequence data have been produced that hold promise for rapid species identification, for example, for biosecurity. The fruit fly tribe Dacini holds about a thousand species, of which 80 are pests of economic concern. We generated a COI reference library for 265 species of Dacini containing 5601 sequences that span most of the COI gene using circular consensus sequencing. We compared distance metrics versus monophyly assessments for species identification and although we found a 'soft' barcode gap around 2% pairwise distance, the exceptions to this rule dictate that a monophyly assessment is the only reliable method for species identification. We found that all fragments regularly used for Dacini fruit fly identification >450 base pairs long provide similar resolution. 11.3% of the species in our dataset were non-monophyletic in a COI tree, which is mostly due to species complexes. We conclude with recommendations for the future generation and use of COI libraries. We revise the generic assignment of Dacus transversus stat. rev. Hardy 1982, and Dacus perpusillus stat. rev. Drew 1971 and we establish Dacus maculipterus White 1998 syn. nov. as a junior synonym of Dacus satanas Liang et al. 1993.

Evaluation of the effect of agroclimatic variables on the probability and timing of olive fruit fly attack.

Agroclimatic variables may affect insect and plant phenology, with unpredictable effects on pest populations and crop losses. Bactrocera oleae Rossi (Diptera: Tephritidae) is a specific pest of Olea europaea plants that can cause annual economic losses of more than one billion US dollars in the Mediterranean region. In this study, we aimed at understanding the effect of olive tree phenology and other agroclimatic variables on B. oleae infestation dynamics in the Umbria region (Central Italy). Analyses were carried out on B. oleae infestation data collected in 79 olive groves during a 7-year period (from 2015 to 2021). In July-August, B. oleae infestation (1% attack) was negatively affected by altitude and spring mean daily temperatures and positively by higher winter mean daily temperatures and olive tree cumulative degree days. In September-October, infestation was negatively affected by a positive soil water balance and high spring temperatures. High altitude and cumulative plant degree days were related to delayed attacks. In contrast, high winter and spring temperatures accelerated them. Our results could be helpful for the development of predictive models and for increasing the reliability of decision support systems currently used in olive orchards.

Stronger interspecific sexual differences may be favored when females search for mates in the presence of congeners.

Why are some species sexually dimorphic while other closely related species are not? While all females in genus Strauzia share a multiply-banded wing pattern typical of many other true fruit flies, males of four species have noticeably elongated wings with banding patterns "coalesced" into a continuous dark streak across much of the wing. We take an integrative phylogenetic approach to explore the evolution of this dimorphism and develop general hypotheses underlying the evolution of wing dimorphism in flies. We find that the origin of coalesced and other darkened male wing patterns correlate with the inferred origin of host plant sharing in Strauzia. While wing shape among non-host-sharing species tended to be conserved across the phylogeny, shapes of male wings for Strauzia species sharing the same host plant were more different from one another than expected under Brownian models of evolution and overall rates of wing shape change differed between non-host-sharing species and host-sharing species. A survey of North American Tephritidae finds just three other genera with specialist species that share host plants. Host-sharing species in these genera also have wing patterns unusual for each genus. Only genus Eutreta is like Strauzia in having the unusual wing patterns only in males, and of genera that have multiple species sharing hosts, only in Eutreta and Strauzia do males hold territories while females search for mates. We hypothesize that in species that share host plants, those where females actively search for males in the presence of congeners may be more likely to evolve sexually dimorphic wing patterns.

Insecticidal effect of new synthesized chalcone derivatives on Caribbean fruit fly, Anastrepha suspensa.

In this present study, new chalcone derivatives were synthesized from 4-aminoacetophenone, which were confirmed by spectroscopic methods. The toxic risks of chalcones to humans and the environment were investigated by a web-based platform called ADMETlab. With this program, the possible toxic effects of the compounds on liver, respiratory system, and eyes were evaluated. For the topical insecticidal activity, adult female Caribbean fruit fly, Anastrepha suspensa, was targeted. Results of the toxicity tests showed that chalcone derivatives are effective against female A. suspensa. Among the synthesized chalcones, 1-(4-cinnamoylphenyl)-3-(p-tolyl)urea (2) exhibited the greatest insecticidal activity, resulting in 73 % mortality at 100 µg/fly after 24 h, whereas other derivatives showed less than 30 % mortality. Our results demonstrate that insecticidal activity may be modulated by the presence of a certain phenyl ring in the structure of derivative 2 and, therefore, has potential for design of efficient chemicals for tephritid fruit fly management.

Toxicity of Beauveria bassiana to Bactrocera dorsalis and effects on its natural predators.

Entomopathogenic fungi (EPF) are economical and environmentally friendly, forming an essential part of integrated pest management strategies. We screened six strains of Beauveria bassiana (B1-B6) (Hypocreales: Cordycipitaceae), of which B4 was the most virulent to Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). We further assessed the biological characteristics of strain B4 and the environmental factors influencing its ability to infect B. dorsalis. We also evaluated the effects of B4 on two of the natural predators of B. dorsalis. We found that strain B4 was the most virulent to 3rd instar larvae, pupae, and adult B. dorsalis, causing mortality rates of 52.67, 61.33, and 90.67%, respectively. B4 was not toxic to B. dorsalis eggs. The optimum B4 effects on B. dorsalis were achieved at a relative humidity of 91-100% and a temperature of 25°C. Among the six insecticides commonly used for B. dorsalis control, 1.8% abamectin emulsifiable concentrate had the strongest inhibitory effect on B4 strain germination. B4 spraying affected both natural enemies (Amblyseius cucumeris and Anastatus japonicus), reducing the number of A. cucumeris and killing A. japonicus adults. We found a valuable strain of EPF (B4) that is virulent against many life stages of B. dorsalis and has great potential for the biological control of B. dorsalis. We also provide an important theoretical and practical base for developing a potential fungicide to control B. dorsalis.

RNA virus diversity and prevalence in field and laboratory populations of melon fly throughout its distribution.

Insects have a rich diversity of RNA viruses that can either cause acute infections or persist in host populations without visible symptoms. The melon fly, Zeugodacus cucurbitae (Tephritidae) causes substantial economic losses through infestation of diverse cucurbit and other crops. Of Indomalayan origin, it is now established in many tropical regions of the world. The virome diversity of Z. cucurbitae is largely unknown across large parts of its distribution, including the Indian subcontinent. We have analysed three transcriptomes each of one field-collected and one laboratory-reared Z. cucurbitae population from Bangalore (India) and discovered genomes of ten putative RNA viruses: two sigmaviruses, one chimbavirus, one cripavirus, one noda-like virus, one nora virus, one orbivirus, one partiti-like virus, one sobemovirus and one toti-like virus. Analysis of the only available host genome of a Hawaiian Z. cucurbitae population did not detect host genome integration of the detected viruses. While all ten viruses were found in the Bangalore field population only seven were detected in the laboratory population, indicating that these seven may cause persistent covert infections. Using virus-specific RNA-dependent RNA polymerase gene primers, we detected nine of the RNA viruses with an overall low variant diversity in some but not all individual flies from four out of five Indian regions. We then screened 39 transcriptomes of Z. cucurbitae laboratory populations from eastern Asia (Guangdong, Hainan, Taiwan) and the Pacific region (Hawaii), and detected seven of the ten virus genomes. We found additional genomes of a picorna-like virus and a negev-like virus. Hawaii as the only tested population from the fly's invasive range only had one virus. Our study provides evidence of new and high RNA virus diversity in Indian populations within the original range of Z. cucurbitae, as well as the presence of persistent covert infections in laboratory populations. It builds the basis for future research of tephritid-associated RNA viruses, including their host effects, epidemiology and application potential in biological control.

First report of the complete mitochondrial genome of Carpomya pardalina (Bigot) (Diptera: Tephritidae) and phylogenetic relationships with other Tephritidae.

Carpomya pardalina is known for its potential invasiveness, which poses a significant and alarming threat to Cucurbitaceae crops. It is considered a highly perilous pest species that requires immediate attention for quarantine and prevention. Due to the challenges in distinguishing pests of the Tephritidae family based on morphological characteristics, it is imperative to elucidate the mitochondrial genomic information of C. pardalina. In this study, the mitochondrial genome sequence of C. pardalina was determined and analyzed using next-generation sequencing. The results revealed that the mitogenome sequence had a total length of 16,257 bp, representing a typical circular molecule. It consisted of 13 PCGs, two rRNA genes, 22 tRNA genes and a non-coding region. The structure and organization of the mitochondrial genome of C. pardalina were found to be typical and similar to the published homologous sequences of other fruit flies in the Tephritidae family. Phylogenetic analysis confirmed that C. pardalina belongs to the Carpomya genus, which is consistent with traditional morphological taxonomy. Additionally, Carpomya and Rhagoletis were identified as sister groups. This study presents the first report of the complete mitochondrial genome of C. pardalina, which can serve as a valuable resource for future investigations in species diagnosis, evolutionary biology, prevention and control measures.

Mitochondrial coding genes mediate insecticide tolerance in the oriental fruit fly, Bactrocera dorsalis (Hendel).

The oriental fruit fly, Bactrocera dorsalis (Hendel), an invasive insect pest infesting fruits and vegetables, possesses a remarkable capacity for environmental adaptation. The investigation of behind mechanisms of the stress adaptability in B. dorsalis holds significantly practical relevance. Previous studies on the molecular mechanism underlying stress resistance in B. dorsalis have predominantly focused on nuclear-coding genes, with limited exploration on organelle-coding genes. In this study, we assessed alterations in the mitochondrial physiological parameters of B. dorsalis under exposure to malathion, avermectin, and beta-cypermethrin at LD50 dosages. The results showed that all three insecticides were capable of reducing mitochondrial complex IV activity and ATP content. Expression patterns of mitochondrial coding genes across different developmental stages, tissues and insecticide exposures were analyzed by RT-qPCR. The results revealed that these mitochondrial coding genes were expressed in various tissues and at different developmental stages. Particularly noteworthy, atp6, cox2, and cytb exhibited substantial up-regulation in response to malathion and avermectin treatment. Furthermore, RNAi-mediated knockdown of atp6 and cox2 resulted in the increased toxicity of malathion and avermectin against B. dorsalis, and cox2 silencing was also associated with the decreased complex IV activity. These findings suggest that atp6 and cox2 most likely play pivotal roles in mediating tolerance or resistance to malathion and avermectin in B. dorsalis. Our results provide novel insights into the role of mitochondrial coding genes in conferring tolerance to insecticides in B. dorsalis, with practical implications for controlling this pest in the field.